Figure 1.
Circular maps of the Cardinium hertigii cEper1 chromosome and plasmid pCher.
The distribution of protein coding genes (CDSs), mobile genetic transposases, genes potentially important for host cell interaction including ankyrin repeat containing proteins, tetratricopetide repeat containing proteins and others, and the genes encoding the putative antifeeding prophage-derived secretion system is shown. The innermost green and violet circles represent the GC-skew (purple: below average, green: above average).
Table 1.
General features of the genome of Cardinium hertigii cEper1 and its closest sequenced relative Amoebophilus asiaticus 5a2.
Figure 2.
Metabolism, transport capabilities, and host cell interaction of Cardinium hertigii cEper1.
All predicted complete metabolic pathways and major transport proteins encoded on the genome are indicated. Cardinium lacks most biosynthetic pathways and imports nearly all essential metabolites from its host cell by employing a variety of transport proteins. Host cell interaction is mediated by secretion of effector proteins although no evidence for known protein secretion systems was found in the genome. A putative antifeeding prophage-derived secretion system could be used for translocation of proteins directly into the insect host cell by a contraction mechanism similar to type VI secretion systems [103].
Figure 3.
The putative phage derived protein secretion system of Cardinium hertigii cEper1.
Electron micrographs showing Cardinium in Encarsia pergandiella ovaries within a nurse cell (A) and a follicle cell (B), respectively. Arrows point to the antifeeding prophage (AFP) like fibril structures in longitudinal view (A) and cross section (B) representing the putative secretion system for translocation of effector proteins into the host cells; bars, 200 nm. (C) A schematic representation of the genomic organization of the AFP-like gene cluster of Cardinium compared to those of Serratia entomophila and Amoebophilus asiaticus. Locus tags and gene names are indicated. Homologous proteins are shown in the same color and connected with grey bars. Genes labeled with an asterisk are conserved among five different Cardinium strains tested by PCR (Tables S5, S6, S7).